The origin of volatile element depletion in terrestrial planets and meteorites relative to a solar composition represented by CI carbonaceous chondrites remains an unsolved problem. The isotope compositions of moderately volatile elements may offer the possibility to distinguish between the various processes that may have caused this depletion (e.g., partial condensation or partial evaporation). We report high precision Sn isotope measurements in carbonaceous chondrites and ordinary chondrites and the results are reported as δ^124/116Sn. Four carbonaceous chondrites (Orgueil CI, Murchison CM2, NWA 5240 CV3 and Allende CV3) show a limited range in δ^124/116Sn (–0.02‰ to 0.11‰) with an average value of 0.04 ± 0.11‰ (2 s.d.) for a wide range of Sn concentrations (0.63 ppm to 1.57 ppm). The absence of Sn isotope fractionation among carbonaceous chondrites suggests that volatile depletion may have taken place under thermodynamic equilibrium conditions between solid and vapor in the Solar Nebula. Alternatively, the mixing of two components, a volatile-free component containing no or little Sn and a volatile-rich component could explain this trend. This latter hypothesis is consistent with the overall trace element pattern found in carbonaceous chondrites, showing a constant relative abundance when normalized to CI chondrites for the most volatile elements. In contrast with carbonaceous chondrites, ordinary chondrites exhibit a larger range of Sn isotope compositions (δ^124/116Sn from –2.02‰ to 0.64‰), but neither the degree of metamorphism (3–6) nor the group (H, L, LL) is correlated with Sn isotopic variations, or with the Sn contents (range 0.20 to 1.44 ppm). Nineteen out of twenty-one ordinary chondrites are enriched in light Sn isotopes compared with carbonaceous chondrites and the bulk silicate Earth. The trace element patterns of volatile elements in ordinary chondrites suggest that equilibrated ordinary chondrites have been disturbed by parent body processes related to metamorphic or shock overprinting but also inherited isotope fractionation found in unequilibrated ordinary chondrites. Last, the isotope composition of the bulk silicate Earth (BSE) indicates that the volatile element depletion observed in the Earth took place in conditions perhaps similar to those of carbonaceous chondrites, as a simple model describing the effect of Earth’s core formation on Sn isotopes shows that the Sn isotope composition of the bulk Earth is identical to that of the BSE and of carbonaceous chondrites.

相对于以 CI 碳质球粒陨石为代表的太阳成分，类地行星和陨石中挥发性元素消耗的起源仍然是一个未解决的问题。中等挥发性元素的同位素组成可以提供区分可能导致这种消耗的各种过程（例如，部分冷凝或部分蒸发）的可能性。我们报告了碳质球粒陨石和普通球粒陨石的高精度 Sn 同位素测量结果，结果报告为 δ ^124/116 Sn。四种碳质球粒陨石（Orgueil CI、Murchison CM2、NWA 5240 CV3 和 Allende CV3）的 δ ^124/116范围有限Sn (–0.02‰ 至 0.11‰) 的平均值为 0.04 ± 0.11‰ (2 sd)，适用于广泛的 Sn 浓度范围（0.63 ppm 至 1.57 ppm）。碳质球粒陨石中没有 Sn 同位素分馏，这表明在太阳星云中固体和蒸汽之间的热力学平衡条件下可能发生了挥发性消耗。或者，两种成分的混合，即不含或几乎不含 Sn 的无挥发成分和富含挥发成分的成分可以解释这一趋势。后一种假设与在碳质球粒陨石中发现的整体微量元素模式一致，当将最易挥发元素归一化为 CI 球粒陨石时，显示出恒定的相对丰度。与碳质球粒陨石相比，普通球粒陨石表现出更大范围的 Sn 同位素组成（δ ^124/116Sn 从 –2.02‰ 到 0.64‰)，但变质程度 (3-6) 和组 (H、L、LL) 都与 Sn 同位素变化或与 Sn 含量（范围 0.20 到 1.44 ppm）无关. 与碳质球粒陨石和大块硅酸盐地球相比，21 个普通球粒陨石中有 19 个富含轻 Sn 同位素。普通球粒陨石中挥发性元素的微量元素模式表明，平衡的普通球粒陨石受到了与变质或冲击叠印相关的母体过程的干扰，但也受到了未平衡的普通球粒陨石中发现的遗传同位素分馏的干扰。最后，大块硅酸盐地球 (BSE) 的同位素组成表明，在地球中观察到的挥发性元素耗尽发生在可能与碳质球粒陨石相似的条件下，